Effects of feeding ursocholic acid to germfree rats.

Germfree rats were fed 24-14C-ursocholic acid (UC) mixed into the diets for 10 days. The bile was then drained by cannulation for 6 hours to collect the bile salt pool. No biotransformation of the labelled UC occurred and it constituted approximately equal to 75% of an enlarged bile salt pool. Less phospholipid and cholesterol were secreted into the bile per mumol bile salt compared to normal rats. The critical micellar concentration (CMC) of the bile was determined by equilibrium dialysis and found to be increased. Faecal excretion of labelled triolein added to the diet was unaffected by feeding ursocholic acid. Excretion of 14C-octadecane and 14C-cholesterol increased significantly under the same conditions. Ursocholic acid feeding thus resulted in a selective malabsorption of octadecane and cholesterol.